This proposal is part of an ongoing effort to characterize, in molecular terms, the human major histocompatibility complex and the products which it encodes. Studies are proposed using the recently cloned HLA specific cDNA fragment as a basis for molecular biological studies on the HLA system. Full length cDNA clones of several HLA antigens will be constructed and analyzed by dNA sequencing. This offers a rapid means of obtaining substantial information on the molecular and genetic basis of HLA variability. In addition, these clones will be used to probe the genomic structure of the HLA region. Radiation induced HLA deletion variants will be used to help characterize the various HLA clones obtained. It is hoped that such an analysis will help in determining which probes are either allelic or locus specific. Genomic libraries from human lymphoblastoid cell lines will be constructed and screened for HLA specific clones. These genomic HLA clones will then be used to construct other probes for genomic "walking" experiments. Genomic "walking" experiments consist of constructing probes from the end regions of a given genomic clone. These probes can then be used to rescreen the genomic library for additional clones containing sequences which overlap with the initial clone. By repeating this probing, one can "walk" or move along the genome from the original clone. The aim of such walking experiments is to obtain clones of other HLA loci. Moreover, HLA genomic clones will provide material for DNA sequence analysis and RNA selection experiments. The mRNA selection studies are aimed at identifying previously undetected genes from the HLA system. It is envisioned that in the long term these techniques will provide a unique approach to studying the molecular basis for the association of some diseases with certain HLA specificities.